The human population continues to expand alarming rates making the development of safer, more economical and effective contraceptives an important health-related goal. In a 1997 survey by the Henry J. Kaiser Family Foundation, more than 66% of respondents believed that men should play a larger role in contraceptive use. The ability to intervene in fertilization could aid couples wanting children, increase reproductive efficiency in endangered species or domestic animals used as food sources, and decrease fertilization rates of certain wild animal populations such as vermin, benefiting the health of millions of people. However, the fertilization process remains poorly understood, leading to severe limitations in development of methods to intervene. The over-all goal of this project is to identify genes critical to sperm behavior and fertilization. The criterion for initial selection of genes relies on cDNA sequences encoding proteins that predict a sperm receptor, channel, transporter, adhesion protein, translocase or ion exchanger, and on genes expressed exclusively in spermatozoa during or after meiosis. Specific Aim 1 centers on the discovery and functional analysis of new sperm candidate genes (lectin-like, single TM potential receptor, chemokine-like tetraspan). They will be targeted for disruption to determine the effects on sperm behavior and fertility. The gene products will be studied to define mechanisms of regulation. Searches will continue for new candidate genes critical to fertility, and the role of a sperm-specific sodium/hydrogen exchanger (sNHE) in capacitation and induction of the acrosome reaction will be delineated. Specific Aim 2 is a detailed analysis of candidate gene product regulation. The sNHE will serve as the primary prototype for other candidate gene products. Studies will concentrate on mechanisms of regulation of the sNHE (e.g. the effects of covalent modification and associated proteins on sNHE activity). Based on these studies, linkage maps will begin to connect pathways from the sNHE, or other candidate gene products, to sperm behavioral responses such as motility activation or induction of the acrosome reaction.